Too expensive; I’d say -15 Power Requirement at the least.

Also. This is steampunk, not magic.

I was discussing with ais, which amount of Gems should be ok. At first, I thought of 2 Gems…

If you weren’t a family member, you could trade 10 Iron and 7 Coal for these 7 Gems. (if you never traded with Purpblebeard that week before or else a bit cheaper.

Also, there is a Part, which costs 5 Iron and has a Power Requirement of 5. Compare this parts. I think, meanwhile, this one is not that expensive.

Additionally, as Kevan stated elsewhere, most Parts should be useless most times. If they weren’t, they would be simply part of each Invention, which wouldn’t mean much fun… So, if you think it’s too expensive, where is the problem with this one?

We already have two Iron-based Parts which do nothing but reduce Power Requirement. I think it’s more interesting if different resources are used for different things.